X-ray windows are used for enclosing an x-ray source or detection device. The window can be used to separate air from a vacuum within the enclosure while allowing passage of x-rays through the window.
X-ray windows can be made of a thin film. It can be desirable to minimize attenuation of the x-rays, especially with low energy x-rays, thus it is desirable that the film is made of a material and thickness that will result in minimal attenuation of the x-rays. Thinner films attenuate x-rays less than thick films, but the film must not be too thin or the film may sag or break. A sagging film can result in cracking of corrosion resistant coatings and a broken film will allow air to enter the enclosure, often destroying the functionality of the device. Thus it is desirable to have a film that is made of a material that will have sufficient strength to avoid breaking or sagging but also as thin as possible for minimizing attenuation of x-rays.
A support structure can be used to support the thin film. Use of a support structure can allow use of a thinner film than could be used without the support structure. For example, a support structure can be made of a plurality of ribs with openings therein. The thin film can be attached to and span the ribs and openings. In order to minimize attenuation of x-rays, it is desirable that the ribs of the structure have a smaller width and height. Wider and higher ribs are typically stronger. Stronger rib materials can provide sufficient strength at a smaller size.
X-ray windows are often used with x-ray detectors. In order to avoid contamination of an x-ray spectra from a sample being measured, it is desirable that x-rays impinging on the x-ray detector are only emitted from the source to be measured. Unfortunately, x-ray windows, including the window support structure and thin film, can also fluoresce and thus emit x-rays that can cause contamination lines in the x-ray spectra. Contamination of the x-ray spectra caused by low atomic number elements is less problematic than contamination caused by higher atomic number elements. It is desirable therefore that the window and support structure be made of a material with as low of an atomic number as possible in order to minimize this noise.